Method for blind rivet welding

ABSTRACT

A blind rivet assembly is inserted through aligned holes provided in a top member and bottom member. The blind rivet includes a rivet head that abuts the top member and a hollow rivet shank integral with the rivet head. A mandrel includes a mandrel stem that extends thorough the hollow rivet and a mandrel head that abuts the terminal end of the rivet shank. A tool holds the rivet head in contact with the top member and forcibly withdraws the mandrel in the direction to exit the aligned holes to thereby cause the mandrel head of axially collapse and radially expand the terminal end of the rivet shank into engagement with the bottom member to thereby attach the top member and the bottom member together. Weld current is then applied to the rivet head to thereby weld the blind rivet in place.

FIELD OF THE INVENTION

The present invention relates to an improved method for blind riveting together a pair of members.

BACKGROUND OF THE INVENTION

It is known to attach together a pair of members using a blind rivet assembly. The use of a blind rivet to attach members together is particularly useful in the assembly or repair of vehicle bodies or other applications in which access can be obtained to only one side of one of the members (a top member), with the other member (a bottom member) being hidden and inaccessible below the top member.

It would be desirable to provide improvements in the blind rivet method of attaching members together. For example, improvements to make such attachments stronger and more vibration proof would be desirable.

SUMMARY OF THE INVENTION

In an improved method of blind rivet fastening aligned holes are provided in the top and bottom members. A blind rivet assembly is inserted through the aligned holes. The blind rivet includes a rivet head that abuts the top member and a hollow rivet shank that is integral with the rivet head and reaches through and beyond the aligned holes and has a terminal end. The blind rivet assembly also includes a mandrel, the mandrel having a mandrel stem that extends thorough the hollow rivet and includes a mandrel head that abuts the terminal end of the rivet shank. A tool holds the rivet head in contact with the top member and forcibly withdraws the mandrel to thereby cause the mandrel head to axially collapse and radially expand the terminal end of the rivet shank into engagement with the bottom member to thereby attach the top member and the bottom member together. Weld current is then applied to the rivet head to thereby weld the blind rivet in place.

Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

FIG. 1 is a section view through a top member and a bottom member that are to be attached together and showing a blind rivet assembly seated in aligned holes in the members;

FIG. 2 is a view similar to FIG. 1 but showing a tool positioned over the blind rivet assembly;

FIG. 3 show that the jaws of the tool have gripped the mandrel of the blind rivet assembly;

FIG. 4 shows that the jaws of the tool have been actuated to withdraw the mandrel and thereby cause the head of the mandrel to expand the rivet shank of the blind rivet into engagement with the bottom member;

FIG. 5 shows that the mandrel has been fractured;

and FIG. 6 shows that weld current has been applied through the tool to weld the blind rivet assembly in place.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Referring to FIG. 1, a top member 10 is a sheet metal panel and a bottom member 12 is a metal tube. The top member and the bottom member are to be attached together.

A hole 14 is drilled, pierced, or otherwise provided through the top member 10 and an aligned hole 16 is provided in the bottom member 12.

A blind rivet assembly 18 is inserted through the aligned holes 14 and 16. The blind rivet assembly 18 includes a blind rivet 22 and a mandrel 24.

The blind rivet 22 has a rivet head 26 and a hollow rivet shank 28 that are integrally formed in one piece. The rivet head 26 rests on the top face 30 of the top member 10. The hollow rivet shank 28 extends through the aligned holes 14 and 16 and is somewhat longer than the combined thickness of the top and member members 10 and 12 and has terminal end 32 that ends somewhat beyond the bottom face 34 of the bottom member 12.

The mandrel 24 includes a stem 38 that extends through the blind rivet 22 and has an enlarged mandrel head 40 at its terminal end. As seen in FIG. 1, the mandrel 24 is longer than the length of the blind rivet 22 so that the stem 38 extends well above the rivet head 26 of the blind rivet 22. The mandrel head 40 is larger than the inner diameter of the hollow rivet shank 28 of the blind rivet 22, but smaller than the diameter of the aligned holes 14 and 16 so that the blind rivet assembly 18 can be inserted through the aligned holes 14 and 16. The mandrel stem 38 has a weakness, particularly a fracture notch at 42 to define a fracture region in the stem 38, as will be discussed hereinafter.

Referring to FIG. 2, a blind rivet installation tool, generally indicated at 48, is used to install the blind rivet assembly 18. The tool includes an anvil 50 in the form of a hollow sleeve and having an anvil end 52 that is pressed against the rivet head 26. A plurality of opposed jaws, of which jaws 54 and 56 are shown in the drawings, are situated within the anvil head 50 and operated by an actuator and collet mechanism, not shown, by which the jaws cooperate to grip the mandrel stem 38 and forcibly withdraw the mandrel stem 38 in the upward direction as viewed in the drawing Figures, as will be discussed hereinafter.

In FIG. 2, the tool is shown with the anvil 50 pressed against the rivet head 26 and the jaws 54 and 56 in open positions surrounding the mandrel stem 38.

FIGS. 3, 4 and 5 show the progressive actuation of the blind rivet installation tool 48 to install the blind rivet assembly 18. In FIG. 3, the jaws 54 and 56 have been partially withdrawn in the upward direction and moved together into gripping relationship with the mandrel stem 38. It will be appreciated that the jaws 54 and 56 are shown with teeth that assure effective gripping of the mandrel stem 38. The mandrel stem 38 may also be provided with grooves, not shown, to further promote gripping by the jaws 54 and 56.

In FIG. 4, the jaws 54 and 56 have been forcibly withdrawn causing the mandrel stem 38 to have been drawn upwardly so that the mandrel head 40 has contacted the terminal end 32 of the rivet shank 28 and worked to axially collapse and radially expand the rivet shank 28 to form an expanded head 60 that engages with the underside 34 of the lower member 12. Thus, the top member 10 and the bottom member 12 are tightly captured between the rivet head 22 and the expanded head 60 of the rivet shank 28, thereby fastening together the top member 10 and the bottom member 12.

In FIG. 5, the jaws 54 and 56 have been further withdrawn so that the mandrel stem 38 has fractured, as facilitated by the fracture notch 42.

Referring to FIG. 6, it is seen that the anvil 50 of the installation tool has an electrical cable 70 attached thereto. The cable 70 connects to a resistance welder 72 so that the anvil 50 serves as an electrode. An electrode 74 is placed against the upper member 10 a short distance from the rivet head 22. Cable 76 connects electrode 74 to the welder 72.

FIG. 6 shows that weld current has been applied to the anvil 50 and to the electrode 74 so that the rivet shank 28 of the blind rivet 22 has become welded by the heat resulting from the conduction of the weld current through the rivet assembly 18 and the top member 10. Accordingly, the blind rivet 22 is held in place, and the upper member 10 and the lower member 12 are connected together, by both the welded connection and by the mechanical clamping of the top and bottom member between the rivet head 26 and the expanded head 60 of the hollow rivet shank 28.

The anvil 50 and the electrode 74 may be a copper material in order to promote the welding process. A person of ordinary skill in the art will recognize that the extent and quality of the weld will be determined by control of the customary welding variables such as the relative thickness and materials of the top and bottom member 10, the size and materials of the blind rivet assembly 18, the distance between the electrodes, the weld current, the duration of the weld current, and the forces with which the electrodes are held against the rivet head 26 and the top member 10 of the weld. Accordingly, in some cases, the weld current may develop material melting and metallurgical bonding between the mandrel 24 and the rivet 22, as well as melting and bonding between the rivet and the top and bottom members 10 and 12.

The forgoing description of the invention is merely exemplary in nature and, thus, variations thereof are intended to be within the scope of the invention. For example, the fracture of the mandrel, as shown in FIG. 6, may occur either before, during, or after the application of the weld current. Furthermore, its is known that blind rivet assemblies are available in many shapes and designs, and the present invention is not limited to the particular style of blind rivet assembly shown in the drawings. In addition, the electrode 74 may be mounted on a common tool support mechanism, not shown, with the installation tool 48 and anvil 50 so that the electrode 74 is forced against the top member 10 simultaneous with the placement of the anvil 50 against the blind rivet head 26. Alternatively, the electrode 74 may be separately moved into contact with the top member 10 by its own support mechanism, not shown. In addition, in that circumstance where the bottom member 12 is accessible, it may be desirable to place the electrode 74 against the bottom member 12 instead of against the top member 10. 

1. A method of blind riveting together a top member and a bottom member provided with aligned rivet holes therein, comprising the steps of: inserting a blind rivet assembly through the aligned rivet holes of the top and bottom members, said blind rivet assembly including a blind rivet and a mandrel, the blind rivet having a rivet head abutting the top member and a hollow shank reaching through the aligned holes of the top and bottom members and having a terminal end, the mandrel including a stem extending through the hollow shank of the rivet and a mandrel head adjacent the terminal end of the rivet shank, forcibly withdrawing the mandrel in the direction to exit the aligned holes to thereby cause the mandrel head to axially collapse and radially expand the hollow shank of the blind rivet into engagement with the bottom member to thereby attach the top member and the bottom member; and applying weld current to the rivet head to weld the blind rivet in place.
 2. The method of claim 1 comprising the further step of fracturing the mandrel stem from the mandrel head after the mandrel head has axially collapsed and radially expanded the hollow shank of the blind rivet
 3. The method of claim 2 further comprising the step of fracturing the mandrel stem after applying the weld current.
 4. The method of claim 2 further comprising the step of fracturing the mandrel stem prior to applying the weld current.
 5. The method of claim 2 further comprising the step of fracturing the mandrel stem during the application of weld current.
 6. The method of claim 1 in which an installation tool for installing the blind rivet assembly includes an anvil that seats on the rivet head and has a welder cable connected thereto so that the anvil functions as an electrode to apply weld current to the rivet head.
 7. The method of claim 6 in which the installation tool includes an electrode that is connected to a welder cable and seats against the top member at a distance from the blind rivet so that weld current is conducted through the blind rivet and through the top member.
 8. A method of blind riveting together a top member and a bottom member provided with aligned rivet holes therein, comprising the steps of: inserting a blind rivet assembly through the aligned rivet holes of the top and bottom members, said blind rivet assembly including a blind rivet and a mandrel, the blind rivet having a rivet head abutting the top member and a hollow shank reaching through the aligned holes of the top and bottom members and having a terminal end, the mandrel including a stem extending through the hollow shank of the rivet and a mandrel head adjacent the terminal end of the rivet shank, applying an installation tool including an anvil seated on the rivet head and jaws for gripping and forcibly withdrawing the mandrel to thereby cause the mandrel head to axially collapse and radially expand the hollow shank of the blind rivet into engagement with the bottom member to thereby attach the top member and the bottom member; applying an electrode to one of the top and bottom members at a distance from the blind rivet, and conducting weld current between the anvil and electrode so that the blind rivet is melted and metallurgically bonded with at least the top member to thereby weld the blind rivet in place.
 9. The method of claim 8 in which the blind rivet is welded to both the top member and the bottom member.
 10. The method of claim 8 in which the mandrel is welded to the blind rivet.
 11. The method of claim 8 in which the electrode is a part of the installation tool so that upon the application of the installation tool to seat the anvil upon the rivet head, the electrode is simultaneously placed against the top member.
 12. The method of claim 8 in which at least a portion the mandrel stem is fractured from the mandrel head.
 13. A method of blind riveting together a top member and a bottom member provided with aligned rivet holes therein, comprising the steps of: inserting a blind rivet assembly through the aligned rivet holes of the top and bottom members, said blind rivet assembly including a blind rivet and a mandrel, the blind rivet having a rivet head abutting the top member and a hollow shank reaching through the aligned holes of the top and bottom members and having a terminal end, the mandrel including a stem extending through the hollow shank of the rivet and a mandrel head adjacent the terminal end of the rivet shank, applying an installation tool including an anvil seated on the rivet head and jaws for gripping and forcibly withdrawing the mandrel in the direction to exit the aligned holes to thereby cause the mandrel head to axially collapse and radially expand the hollow shank of the blind rivet into engagement with the bottom member to thereby attach the top member and the bottom member, said installation tool further including an electrode that seats against the upper member at a distance from the rivet head; and conducting weld current between the anvil and electrode so that the blind rivet is melted and metallurgically bonded with the top member and the bottom member so that the weld assists the blind rivet in attaching the top and bottom members together.
 14. The method of claim 13 in which the installation tool also causes a fracture of at least a portion of the mandrel stem from the mandrel head.
 15. The method claim 14 in which the fracture of the mandrel stem occurs one of either before, during or after the application of the weld current.
 16. The method of claim 13 in which the weld current causes the mandrel head to become welded to the blind rivet.
 17. The method of claim 13 in which the weld current causes the rivet shank to become welded to at least one of the first member and second member.
 18. The method of claim 13 in which the weld current welds the rivet shank to the first member and the second member.
 19. The method of claim 13 in which the anvil of the installation tool is constructed of a copper-based alloy. 